The primary trust of the Specialized Population Research Center is to investigate mechanisms concerned with regulation of gonadal function. Most of the fundamental studies are directed towards questions of relevance to work dealing with development of contraceptives. Applied studies deal directory with investigations of the feasibility of using hormonal preparations for male contraception and with problems related to diagnosis and treatment of gonadal disorders. To approach the question of contraception in a scientifically valid and clinically safe way a body of fundamental knowledge concerned specifically with mechanisms involved in regulation by the gonadal steroids of gonadotropin synthesis and release, with the role of gonadotropins and steroids in gonadal function and with the biochemical mechanisms of gonadotropins, androgen, and estrogen action needs to be accumulated. The studies proposed in this application will be directed towards acquisition of this knowledge and elucidation of these mechanisms.